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B. P. Brooks, V. Camasamudram, F. Onojafe, Y. Sergeev, E. Boobalan, K. Tang, H. Liu, C.-H. Xia, X. Gong, R. Alur; Molecular Mechanism of PAX2/Pax2 Missense Mutations in Mouse and Human. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2603.
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The murine Pax2 mutation was identified using standard genetic mapping and DNA sequencing. Heterozygous & homozygous mutant embryos/mice were comprehensively phenotyped. Analysis of structural changes of Pax2/PAX2 due tomutations was performed in silico. In vitro measurements of wild-type and mutant Pax2 protein and mRNA expression, transactivation, sub-cellular localization, DNA binding & protein stability were examined.
A p.T74A mutation in Pax2 leads to developmental ocular and kidney, but not midbrain, abnormalities, similar to previously-reported in knock-out mouse models & humans with PRS. This mutation, along with the two other mutations reported in humans, (p.G75S and p.dup73ET) is predicted to disrupt critical hydrogen bonds in the Pax2 homeodomain. All 3 mutations lead to decreased steady-state levels of Pax2 protein in vitro & a commensurate decrease in transactivation, but do not affect protein localization or DNA binding. The reduction in steady-state protein levels is not due to mRNA stability.
Reduced Pax2/PAX2 protein stability is the molecular mechanism responsible for the PRS phenotype caused by the characterized missense mutations. Our murine model will enable us to investigate how mutant Pax2 protein interacts with other components of the transcriptional apparatus.
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